Situation before installing a CHP unit
A classical energy system contains a water-heating boiler intended for generation of thermal energy for heating and preparation of domestic water. Another option is the use of a hot water storage tank, which serves to accumulate heat during shorter periods of power outage or reduced consumption.
Electricity demand is covered by supply from the electricity grid.
 Situation before installing a CHP unit |
Situation after installing a CHP unit
The rated power of a CHP unit is sized according to the demand of the heat consumer. A combined heat and power system can be defined as a highly efficient system only when the generated energy, including thermal, is fully utilised. Considering heat demand characteristics (Q-h diagram), a CHP unit of lower heat power can be installed in an existing system to cover heat demand throughout the year (up to 7500 hours/year), or a unit of higher heat power to cover heat demand mainly during the heating season (up to 4000 hours/year).
 Q-h diagram |
For greater flexibility in heat and power generation, two or more CHP units of equal or different rated power can be installed in the energy system.
To cover peak heating powers, the system must also include a classical hot water boiler for heat generation, i.e., a so-called peak boiler. The boiler may also be used for heat generation in case of a repair intervention on the unit or when the CHP unit is not in operation due to a too low a heat consumption rate. A peak boiler can be sized either only to the difference between the maximum power of the boiler room and the rated power of the CHP unit or to the full maximum power of the boiler room. The system can also operate without a peak boiler, but in such cases, heat consumption must be constant and oscillation-free.
 Situation after installing a CHP unit |
Options for electricity consumption
In most cases, the generated electricity is given away to the electricity grid. In case of greater demand, it can also be used for personal consumption. In the first case, the state's subsidy for the sale of electricity is obtained through guaranteed purchase, and in the second case, through operating support.
Options for heat consumption
The generated heat, mainly in the form of hot water with the temperature of up to 90°C, is distributed to consumers through a distribution system. The heat can be used to heat rooms, for hot domestic water preparation and for various technological processes. | 
